Comparison of four technical lignins as a resource for electrically conductive carbon particles

Carbon microparticles were produced from different technical lignins, i.e., kraft lignin, soda lignin, lignosulfonate, and organosolv lignin, at different carbonisation temperatures (800 °C, 1200 °C, 1600 °C, and 2000 °C). Before carbonisation, oxidative thermostabilization was performed. The combination of thermostabilization and carbonisation led to a high mass loss and shrinkage, but no major effect on the particle morphology was apparent. The carbon particles obtained from all four lignin variants developed disordered graphitic structures at high carbonisation temperatures, and good electrical conductivities in the carbon powders were observed for all lignin variants, with the exception of lignosulfonate. The polycaprolactone composite films filled with 30% lignin-derived carbon exhibited various conductivities, with the best results achieved using the kraft lignin-derived carbon.